Hand-held surgical staplers have been in use for some time. These staplers feature a magazine to store staples prior to dispensing, a mechanism to feed staples, and another mechanism to form them as they are discharged from the apparatus.
From an ergonomic point of view, the hand-held stapler needs to have a low distal profile to allow the surgeon maximum visibility of the closure site as the staples are formed to close in incision. Another important criteria for surgical staplers is the ability to reliably feed staples as needed without clogging or jamming. The need to reliably feed staples exists concerning the first staple to be fed in a series all the way down to the last remaining staple in the magazine.
Another desirable feature would be an interchangeable feature allowing different nose assemblies to be used with a trigger assembly to facilitate continuing use of the apparatus during a closure procedure. The interchangeable feature also allows flexibility in production since a nose assembly would be usable with a variety of handle assemblies. This advantageous feature is incorporated in the apparatus of the present invention. Also, a feature of the apparatus of this invention is a layout of the staple track permitting a narrow or distal profile promoting visibility of the incision. The staple delivery method has been improved to reliably feed staples down to the last staple in the track so that the apparatus functions reliably.
The apparatus of the present invention is configured to allow maximum wound site access and staple visibility during placement and formation of the staple. The apparatus has a capacity for storage of a large number of staples which is a practical convenience for the surgeon. Due to the overall simple design of the stapler of the present invention, it can be economically built for reliable operation. Compactness of the rotating head stapler of the present invention, especially at the distal end, is a significant attribute.
The apparatus contains a high capacity staple track. The staples are stacked against each other on end to allow storage of as many staples as possible in a compact space. Some prior art designs stored the staples laying on their sides flat, as on a table, one behind the other. When stored in such manner, the capacity of a stapler is significantly reduced. To ensure compactness in the apparatus of the present invention, the staple track is oriented back along a plane roughly parallel to the form tool plane. To form the staples, they must be oriented into the firing position where the form tool can move them against the anvil for staple formation.
To this end, the apparatus of the present invention involves a unique manner of reorienting the staples into the firing position. To do this, the staples must be moved around a curved portion at the distal end of the staple track and through an opening into the path of the form tool. To accomplish this in the prior art, the staple pusher has been made flexible so that the last few staples can be pushed around the curved portion of the staple track. The staple pusher has to be flexible enough to move in the curved portion of the track. While use of a smaller radius at the distal portion of the staple track reduces the distal profile of the stapler, it creates more difficulties in producing a staple pusher flexible enough to traverse the smaller radius curves without excessive friction.
The approach in the prior art has been to utilize a relatively large radius at the distal end of the staple track and to orient the staple track in an angled manner of approximately 15.degree. from the form tool plane. This resulted in a very bulky rotating distal portion. Another problem with the use of fairly small radiuses at the distal end of the staple track is that the staples in the track are pre-loaded toward the distal end of the track. One way to accomplish the pre-load is to locate a compression spring at the proximal end of the staple stack. It then follows that the pre-load will be at its lowest for the last few staples in the stack. If this decrease in pre-load for the last staples is coupled with the need to advance those last staples around a fairly small radius bend, a significant design constraint is presented for staplers of the prior art. The stapler of the present invention has solved this problem by virtue of its features disclosed with regard to the sloping of the staple track with respect to the form tool path. The sloping of the staple track allows the staple cover to be thinner at its distal end. This reduces the height that the staples must be picked up at the distal end of the staple track to get them into the form tool path. It is this feature, coupled with the staple pusher incorporating a "fin" design, that allows the apparatus of the present invention to reliably feed all of the staples in the track into the form tool path. The fin is uniquely shaped to reliably feed up to the last staple and the staple pusher is configured so that the fin is deflected out of the form tool path by the advancing form tool.
By providing these features, the stapler of the present invention overcomes the design limits of prior designs in solving the problem of being able to reliably feed staples up to the last staple in a feed path involving a small radius bend at the distal end of the staple track.
Prior designs of surgical hand-held staplers are illustrated in U.S. Pat. Nos. 4,951,860; 4,662,555; and 4,807,628. These patents show staples stored on a track being fed into a feedpath and finally pushed against an anvil where they are formed and ejected from the stapler.
FIGS. 3 and 4 of U.S. Pat. No. 4,662,555 illustrate a feature which requires completed motion of the trigger handle in either direction before it can be reversed. With this feature, the trigger must be depressed completely before it is allowed to be returned to its neutral position. This allows the surgeon some flexibility while the staple is not fully formed to position the gun prior to full closure of the staple. The requirement that the trigger must come all of the way out before the next cycle can begin prevents misfeeding of staples into the staple track.
Other hand-held surgical staplers having one or more of these features can be seen in U.S. Pat. Nos. 4,391,402; 4,196,836; 4,592,498; 4,523,695; 4,598,711; 4,049,177 (tag attaching apparatus); and European Patent Application 0040157.
Also, of general interest in the attachment art, are U.S. Pat. Nos. 4,077,557 (illustrating a tool used in producing printed circuit assemblies); 4,125,215 (showing a tag attachment apparatus); and 2,228,778 (illustrating a desktop stapler).